1. Field of the Invention
This invention relates to the manufacture of butanedicarboxylic acid esters by the cobalt catalyzed carboalkoxylation of butadiene in the presence of a nitrogen base and, more particularly, to the use of increased amounts of the cobalt catalyst relative to butadiene and base to permit operation at reduced pressure and to simplify the overall process.
2. Description of the Prior Art
The cobalt catalyzed carboalkoxylation of butadiene to produce dicarboxylic acid esters as the principal reaction products has been described in the literature. U.S. Pat. No. 4,169,956, issued on Oct. 2, 1979, describes a typical stepwise carbomethoxylation of butadiene initially to methylpentenoate and then to dimethyladipate employing pressures in the range 300-2000 atm and approximately 0.01-0.1 mole of cobalt per mole of butadiene.
U.S. Pat. No. 3,481,975, issued on Dec. 2, 1969, describes a process for preparing dicarboxylic acids in one step by reacting butadiene, carbon monoxide and water at a pressure of 430 atm using relatively large amounts of dicobalt octacarbonyl but the selectivity to adipic acid is low.
A general discussion of the hydroesterification of butadiene is contained in the article entitled The Cobalt Carbonyl-Catalyzed Hydroesterification of Butadiene With Carbon Monoxide and Methanol, Akio Matsuda, Bulletin of the Chemical Society of Japan, Vol. 46, 524-530 (1973). Hydrocarboxylations and hydroesterifications employing cobalt catalysts are discussed in the article Mechanistic Pathways in the Catalysis of Olefin Hydrocarboxylation by Rhodium, Iridium, and Cobalt Complexes, D. Forster et al., Catal. Rev. - Sci. Eng. 23(1&2) p. 89-105 (1981).
The preparation of the esters of 3-pentenoic acid using cobalt catalysts is disclosed in German Pat. No. DE 3040432, published on June 19, 1981. The production of 3-pentenoic acid is discussed in an articles by Imyanitov et al., Karbonilirovanie Nenasyshchennykh Uglevodorodov (1968) 225-32, 232-43, CA 71 21648y-21649z, a portion of which former disclosure appears in U.K. Pat. No. 1,092,694 published on Feb. 4, 1965. The reaction was studied in a pyridine solvent with cobalt carbonyl catalysts under a pressure of 120-500 atmospheres.
Variations in the reaction conditions employed for the carboalkoxylation are disclosed in U.S. Pat. Nos. 4,171,451, issued on Oct. 16, 1979; 4,310,686, issued on Jan. 12, 1982 and 4,258,203, issued on Mar. 24, 1981. U.S. Pat. No. 4,259,520, issued on Mar. 31, 1981 teaches that butadiene must be removed before the carboalkoxylation of the pentenoate.